Device for artificial respiration with an endotracheal tube

ABSTRACT

A device for ventilation, comprising  
     a ventilator for providing a stream of gas for ventilation at an outlet,  
     a hose for inspiration air one end of which is connected to the outlet,  
     a double-lumen endotracheal tube one lumen of which, at its end distal to the patient, is connected to the other end of the hose for inspiration air,  
     flow meters for measuring the streams of gas in the two lumina of the endotracheal tube,  
     pressometers for measuring the pressures at the ends distal to the patient of the two lumina,  
     an evaluation means for determining the flow resistance in a lumen flowed through by gas because of the stream of gas measured therein and the pressures measured, and  
     a means for outputting an information about the flow resistance of the lumina.

[0001] The invention relates to a device for ventilation via anendotracheal tube.

[0002] The predominant majority of patients being ventilated during anintensive-care therapy or anaesthesia have their airway secured by anendotracheal tube. To this end, an endotracheal tube which consists of aplastic or rubber tube, as a rule, is introduced into the tracheathrough the mouth or nose or by a making an incision in the trachea(“tracheotomy”). At the tracheal end, the endotracheal tube mostly isprovided with a inflatable endotracheal tube “cuff” which seals thetrachea, permits ventilation at an excess pressure, and protects theairways from the penetration of foreign matter. The end distal to thepatient of the endotracheal tube is coupled to a ventilation device viaa hose system. At the point of transition from the endotracheal tube tothe hose system, there is an Y connection piece which has connectedthereto an inspiratory hose and an expiratory hose or expiratory valveleading to the atmosphere.

[0003] A respiratory air filter can be disposed between the endotrachealtube and the hose system to minimize the exchange of micro-organisms andother contaminants between the patient and hose system. The extension oftime intervals between the exchanges of the hose which becomes possiblethereby is advantageous both economically and ecologically. Further,heat-and-moisture exchangers may be provided between the hose system andthe endotracheal tube which cause the inspiration air to be humidifiedto prevent the patient's airways from becoming parched. This isaccomplished by condensing the moisture contained in the expiration airon specific filter-like materials and re-evaporating the moisture duringthe succeeding inspiration. Further, there is a so-called “activehumidification” via a heated evaporator in the inspiratory hose of thehose system.

[0004] The lungs effect an exchange of gas with the external air in apendular process. At this stage, whenever an inspiration takes place gaswhich has been left behind from prior expiration in the so-called “deadspace” first gets into the lungs. The dead space is the entirety of allair conductors which are flowed through during both inspiration andexpiration. It comprises the bronchi and trachea as well as theconventionally single-lumen endotracheal tube and any precedingbreathing air filters or heat-to-moisture exchangers. It ends in anY-connector which ramifies the airway for inspiration and expiration.

[0005] The respiratory excursions subject the lungs to mechanical loadsand require the spontaneously breathing patient to do breathing effort.Since the dead space (both anatomical and device-related) can constitutea significant percentage of the respiratory stroke (about 30% to morethan 50%) its minimization is an important step towards reducing suchloads and breathing effort fractions. A known action to reduce the deadspace is to insert an endotracheal tube having two lumina (a“double-lumen endotracheal tube”) which are separately connected to theinspiratory hose and expiratory hose or the expiratory valve leading tothe atmosphere. A ventilation system having a double-lumen endotrachealtube is described in DE 25 35191 A1, for example. In a double-lumenendotracheal tube, a separator for the inspiration and expiration legsof the ventilation device is installed in lieu of a connection piece forthe two lumina. It is located deeply in the trachea at the tracheal endof the endotracheal tube. Accordingly, this reduces the dead space ofthe system and the breathing effort which caused by the dead space.

[0006] Another advantage of double-lumen endotracheal tubes is providedwhen there is a pressure-regulating ventilation. During such aventilation, the ventilator aims at regulating the pressure at the Yconnection piece. To this end, the common ventilators do not carry out apressure tap which is separately led up to the Y connection piecebecause the pressure prevailing there can be measured just as well viathe upright gas column of the hose which is just not flowed throughduring the respective respiratory phase. When a double-lumenendotracheal tube is used the Y connection piece and, hence, theregulation point will be shifted into the trachea. As a directconsequence, the patient need no longer overcome that part of breathingeffort which is caused by the flow resistances in a single-lumenendotracheal tube. The task of overcoming the flow resistances of thedouble-lumen endotracheal tube is automatically imposed on theventilator.

[0007] When the endotracheal tube kinks or foreign matter such assecretions from the trachea settle(s) in its interior its resistancewill increase. This can cause a hazard to the patient because it willimpede its ventilation and/or high pressures will build up in the lungs(with restriction being preponderant to expiration). Since such changesoccur to the portion of the endotracheal tube that cannot be seen in avisual inspection only late signs will be noticed, i.e. reductions toventilation or pressure rises.

[0008] These disadvantages can be overcome to a limited extent bymonitoring the pressure at the Y connection piece and the gas flows.However, such monitoring cannot discriminate or associate the mechanicalproperties of the structures beyond the Y connection piece (filter,endotracheal tube, airways, lungs, surrounding tissue, muscle activity).Therefore, monitoring the tube properties is only possible to a verylimited extent and only major changes are detected, if at all.

[0009] Another problem is posed by the necessity for constanthumidification of the patient's inspiration air because the endotrachealtube keeps it away from the natural humidifiers (the mucosae of the noseand pharynx). Heat-and-moisture exchangers, as a rule, simultaneouslyfunction as filters, thus forming a contaminant barrier between thepatient and the hose system. However, they require to be alternatelyflowed through by expiration and inspiration air to satisfy theirfunction. Therefore, they cannot be employed for double-lumenendotracheal tubes. At present, if double-lumen endotracheal tubes areused it is only possible to actively humidify such air by means ofelectrically heated evaporators.

[0010] Another problem is how to remove secretions and foreign matterfrom the endotracheal tube. While a ventilation therapy is performed thenatural cleaning mechanism of the airways is capable of transportingsecretions and foreign matter into the trachea up to the endotrachealtube, if at all. They have to be drawn off not later than from thispoint. To this end, it is usual to disconnect the Y connection piecefrom the endotracheal tube so permit a suction catheter to be introducedinto the endotracheal tube. This interrupts ventilation and anycontinuously positive airway pressure (CPAP) or positive end-expiratorypressure (PEEP), which is a common prophylaxis against the collapse ofdiseased parts of the lung, cannot be maintained. Therefore, specialinflation manoeuvres become necessary after this suction to re-opencollapsed parts of the lungs.

[0011] Furthermore, it has been known already to introduce the suctioncatheter through a particular angled adapter, which forms a seal aroundthe catheter, between the endotracheal tube and the Y connection piece.The ventilator remains connected to the endotracheal tube andventilation can be continued, on a principle. However, problems willarise by the fact that the portion of the lumen that is responsible forventilation is reduced in dependence on the dimensions of theendotracheal tube and suction catheter and, as a consequence, itsresistance to both inspiration and expiration air is more or lessincreased. Recent studies have shown that continuing a volume-controlledventilation should be avoided in any case under these circumstances:Hazardous positive or negative pressures are possible, which depend onthe pattern of ventilation and the different dimensions of the hose.Therefore, if ventilation is to be continued under a suction this hasdefinitely to be done in a pressure-regulated mode. Even then, if aconventional single-lumen endotracheal tube is used the pressure in thetrachea will always be distinctly below the target pressure settingduring a suction because there is the endotracheal tube with its reducedlumen between the trachea and the Y connection piece, the point ofmeasurement and regulation.

[0012] DE 195 28113 A discloses a ventilation device for the controlledmechanical ventilation of patients including a measurement andevaluation of the expiratory time constant of the respiratory system.Characteristic changes of the time constant-to-volume relationship aresupposed to allow the detection and differentiation of elevatedresistances or obstructions of the endotracheal tube, on one hand, andthose of the trachea and bronchi, on the other.

[0013] GB 2 318 518 discloses a double-lumen endotracheal tube in whichone lumen serves for the supply of a continuous flow of fresh gas andthe larger lumen serves for discontinuous expiration. Controlledventilation is effected by a phased closure of the larger lumen. Theexpiration limb of the device has connected thereto a pressure sensor.

[0014] U.S. Pat. No. 3,102,537 A discloses a respiration device with aface mask, particularly for air and space travel, which ensures improvedtransfer of moisture from the expired air to the inspired air and amaximum saving of oxygen or another inspired gas from an externalsource. A common wall permeable to moisture is disposed between theexpiration and the inspiration air conduit. In addition, there is areservoir which is passed in by a first portion of the expired gas inorder to be inspired first during the following inspiration.

[0015] Accordingly, it is the object of the invention to provide anoperatively improved device for ventilation via an endotracheal tube.

[0016] The object is achieved by a device for ventilation having thefeatures of claim 1. The device has

[0017] a ventilator for providing a stream of gas for respiration at anoutlet,

[0018] a hose for inspiration air one end of which is connected to theoutlet,

[0019] a double-lumen endotracheal tube one lumen of which is distallyconnected to the other end of the inspiratory hose,

[0020] flow meters connected to the ends distal to the patient of thetwo lumina for measuring the streams of gas in the two lumina of theendotracheal tube,

[0021] pressometers connected to the ends distal to the patients of thetwo lumina for measuring the pressures at the ends distal to the patientof the two lumina,

[0022] an evaluation means for determining the flow resistance in alumen which is flowed through by gas on the basis of the stream of gasmeasured therein and the pressures measured, and

[0023] a means to output an information about the flow resistance of thelumina.

[0024] The invention relies on the possibility of determining the flowresistance in the lumen which is flowed through by gas from the valuesmeasured for the stream of gas resistance in the lumen which is flowedthrough by gas and the pressures prevailing at the two lumina. Namely,the pressometer connected to the end distal to the patient of the lumenwhich is flowed through by gas measures the pressure directly at the enddistal to the patient of this lumen and the pressometer connected to theend distal to the patient of the lumen which is not flowed through bygas measures the pressure at the tracheal end of the lumen which isflowed through so that the pressure loss of the lumen which is flowedthrough results from the two pressures. Then, the flow resistance of thelumen which is flowed through can be calculated, along with the streamof gas passing through the lumen which is flowed through. For thispurpose, reference is made to the interconnections known from the fluidmechanics between the pressure loss, volumetric flow, and flowresistance coefficient of tubes which are flowed through. The flowresistance, in turn, allows to directly conclude therefrom whether theendotracheal tube is inadmissibly kinked or clogged so that correctiveactions are required. In a software-controlled device for ventilation,the evaluation and display procedures described can be easilyimplemented under a software control.

[0025] The rule for all of the inventive devices for ventilation is thatthe lumen for expiration may be connected to the atmosphere via a valve,preferably an actively controlled valve, or may be connected to an inletof the ventilator for expired breathing air via an expiratory hose. Theformer may be the case particularly for emergency ventilators. It iscommon specifically for anaesthesia ventilation that the expired air isreturned to the ventilator if gases which are relatively expensive arefed to the ventilation system and a recovery of the gases from theventilation system is beneficial.

[0026] The flow meters and/or pressometers can be located on theventilator and/or at the end of the tracheal tube. Preferably, they areon the ventilator because if they were disposed at the end of thetracheal tube they would make it more difficult to handle them. If theexpiratory end of the endotracheal tube is not connected to theventilator via an expiratory hose it is obligatory to arrange the flowmeter and pressometer of the expiratory end on the endotracheal tube.Also in such case, however, it is preferred to locate the flow meter andpressometer of the inspiratory end in the ventilator.

[0027] Basically, the device determines the flow resistance of the lumenwhich is flowed through by gas and the hose connected thereto towardsthe ventilator. If the properties of the hose with no endotracheal tubeare known to the device it can determine the flow resistance of theendotracheal tube. For a determination of the properties of the hose, itcan be disconnected from the endotracheal tube and can be opened to theatmosphere or two hoses can be connected to each other and be flowedthrough by streams of gas. If the hose is opened to the atmosphere thepressure loss can be determined by means of the ambient pressure, whichis known, and the pressure measured at one hose end and the stream ofgas which was measured. When the hoses are connected to each other thepressures measured at the ends of the hoses are incorporated into thecalculation. Preferably, there are valve means between the endotrachealtube and the hose/hoses to connect the hose/hoses to the environmentand/or to each other.

[0028] Furthermore, the object is achieved by the device for ventilationaccording to claim 4. The device has

[0029] an endotracheal tube and

[0030] at least one membrane permeable to water in a wall between twolumina of the endotracheal tube and/or between two hoses for connectingthe endotracheal tube to a ventilator.

[0031] The moisture from the expired air condenses on the side of thewater-permeable membrane that forms part of the expiration air limb inorder to be re-absorbed by the dry inspired air on the other side of themembrane that forms part of the limb for inspiration air. Since theexchange of moisture takes place in a counter-current it can becomehighly effective if suitable dimensions are chosen. Efficiency can beimproved by heating the stream of gas in the limb for inspiration airbecause warm gas will take up moisture more rapidly and better.Likewise, it is possible to enhance efficiency by using a membranematerial which preferably transports water from the expiratory limb tothe inspiratory limb. Such “asymmetric” materials are known to be usedin sanitary products (sanitary towels or baby's diapers), for example. Alarge exchange surface can also be achieved by causing the hoses and/orlumina of a double-lumen endotracheal tube to envelope each other, e.g.by surrounding each other concentrically.

[0032] It can also be beneficial to combine the second solution with thefirst solution. This also applies to any aspects of the first and secondsolutions.

[0033] According to an aspect, the device for ventilation has

[0034] a ventilator for providing a stream of gas for ventilation at anoutlet,

[0035] a hose for inspiration air one end of which is connected to theoutlet,

[0036] a double-lumen endotracheal tube one lumen of which is distallyconnected to the other end of the inspiratory hose,

[0037] pressometers for measuring pressures at the ends of the twolumina distal from the patient,

[0038] a closable opening at the distal end of the lumen for the expiredstream of gas to sealingly introduce a suction catheter up to thetracheal end of this lumen, and

[0039] a means for regulating the pressure to a predetermined value inthe lumen which is not flowed through by the gas.

[0040] Pressure-regulated ventilation via the double-lumen endotrachealtube may re readily continued under a suction with no positive ornegative pressures occurring because the ventilation pressure isregulated just in the place where suction also makes itself felt, i.e.in the trachea. The means for pressure regulation is connected to thepressometers and controls the stream of gas. The ventilation pressurecan further be controlled by a valve at the end distal to the patient ofthe lumen for expiration. The control of the pressure via the stream ofgas presupposes that the inspiratory limb of the device, i.e. the hoseand the lumen via which the stream of gas is fed for ventilation, doesnot exert too much resistance to the flow to prevent the ventilationdevice from building up the desired pressure in the trachea.Introduction of the suction catheter into the lumen through which theexpiratory air is discharged avoids a disadvantageous increase in flowresistance in the other lumen.

[0041] It is preferred to additionally design the lumen for the expiredstream of gas with a larger cross-section than has the lumen for thestream of gas für ventilation (asymmetric double-lumen endotrachealtube). The arrangement of the suction catheter could result in areduction of expiration; however, this effect is alleviated oreliminated by the suction stream of gas which also causes some sort ofexpiration (passing by the ventilator). The pressure range predeterminedby the user is not exited at any time in any case. For the first time,this allows to carry out a ventilation therapy during which the pressurenever drops below the predetermined CPAP or PEEP (see above), even inconnection with suction manoeuvres.

[0042] According to an aspect, the device for ventilation has

[0043] a ventilator to provide a stream of gas for ventilation at anoutlet,

[0044] a hose for inspiration gas one end of which is connected to theoutlet,

[0045] a double-lumen endotracheal tube one lumen of which is connectedto the other end of the hose for inspiration gas at the end distal tothe patient, and

[0046] a device for applying an oscillating pressure to the end distalto the patient of the endotracheal tube lumen connected to the hose forinspiration air.

[0047] Applying a high-frequency pressure oscillation to the inspiratorylimb of the ventilator improves the exchange of gas with the patient.This allows to reduce the stream of gas for patient ventilation. In thiscontext, “high-frequency” denotes frequencies which exceed the breathingfrequency of the patients, particularly frequencies which amount to atleast more than 5 Hz. The application of a high-frequency pressureoscillation has admittedly been known in connection with single-lumenendotracheal tubes. However, since the dead volume is considerablepressure fluctuations of a high energy have to be applied here toachieve an improvement to gas exchange. The provision of suitableoscillators poses a problem. When used in conjunction with adouble-lumen endotracheal tube, an improvement to gas exchange isachieved already by means of oscillators which exhibit relatively lowenergies and amplitudes because the dead volume is reduced very much.The propagation of pressure fluctuations into the lungs can be enhancedby configuring the lumen for expiration as a low pass type for pressureoscillation. Preferably, the expiratory limb of the ventilation devicecontains an active valve the actuation of which is coordinated with theoscillation of the pressure generator.

[0048] The invention will be described below with reference to theaccompanying drawing which schematically shows an embodiment.

[0049] The device for ventilation comprises a ventilator 1 with anoutlet 2 at which a stream of gas is provided and an inlet 3 to which astream of expired gas can be fed. At the inlet 3, the ventilator 1 hasan active valve which is closed during inspiration in order to maintainthe pressure in the lungs, and which is opened during expiration. Behindthe valve, the expired gas can be released to the environment.Alternatively, the stream of expired gas can be prepared for reuse inthe ventilator 1 (by removing the CO₂) and the gas needed forventilation will be re-supplied to the outlet where fresh ventilationgas can be admixed.

[0050] Further, there is an endotracheal tube 4 which has two lumina 5,6. At its tracheal end, this double-lumen endotracheal tube 4 has aninflatable cuff 7 which provides a seal towards a trachea 8, theendotracheal tube 4 being advanced up to a point just in front of thebronchi 9.

[0051] The ventilator 1 is connected to the end distal to the patient ofthe endotracheal tube 4 via a hose system 10. The hose system 10 has aninspiratory hose 11 which is connected to the outlet 2 and lumen 5. Itfurther has an hose 12 for expiratory gas which is connected to thelumen 6 and inlet 3.

[0052] The ventilator 1 houses flow meters for measuring the streams ofgas from the outlet 2 and into the inlet 3. The ventilator I also housespressometers for measuring the pressure at the outlet 2 and inlet 3.

[0053] Using the aid of the gas flow and pressure values, a computerintegrated in the ventilator calculates the flow resistance each in thelumens 5 and 6 which are just flowed through by gas. If admissible limitvalues are exceeded the endotracheal tube 4 is assumed to be kinked orclogged and an optical or acoustic signal is emitted.

[0054] Furthermore, the wall between the two lumina 5, 6 is designed asa membrane 13 which is permeable to water in an area. This membrane 13causes moisture to be transmitted from the expiration air in the lumen 6to the inspiration air in lumen 5.

[0055] Furthermore, the lumen 6 is closed by an opening 14 through whicha suction catheter can be sealingly introduced, if required, up to thetracheal end of the endotracheal tube 4. Since the pressure is measuredat the outlet 2 and inlet 3 and the streams of gas are regulated in theventilator 1 the effect is that the pressure in the trachea ismaintained at a constant level.

[0056] Finally, a means for generating a, pulsating pressure which has afrequency exceeding the breathing frequency can be disposed in theventilator 1 and acts upon the outlet 2 to intensify the exchange of gasduring ventilation.

1. A device for ventilation, comprising a ventilator (1) for providing astream of gas for ventilation at an outlet (2), a hose for inspirationair (11) one end of which is connected to the outlet (2), a double-lumenendotracheal tube (4) one lumen (5) of which, at its end distal to thepatient, is connected to the other end of the hose for inspiration air(11), flow meters connected to the ends distal to the patient of the twolumina (5, 6) for measuring the streams of gas in the two lumina (5, 6)of the endotracheal tube (4), pressometers connected to the ends distalto the patient of the two lumina (5, 6) for measuring the pressures atthe ends distal to the patient of the two lumina (5, 6), an evaluationmeans for determining the flow resistance in a lumen (5, 6) flowedthrough by gas because of the stream of gas measured therein and thepressures measured, and a means for outputting an information about theflow resistance of the lumina (5, 6).
 2. The device according to claim 1wherein the flow meters and/or pressure sensors is/are integrated in theventilator (1).
 3. The device according to claim 1 wherein valve meansof the hose/hoses are connected with the environment and/or with eachother between the hose/hoses and the endotracheal tube (4).
 4. A devicefor ventilation, comprising a double-lumen endotracheal tube, at leastone membrane permeable to water in a wall between two lumina of theendotracheal tube that preferably passes water from the side to which astream of expired gas is applied to the side to which a stream ofventilation gas is applied.
 5. The device according to claim 4 which hasa means for heating the stream of ventilation gas.
 6. The deviceaccording to claim 4 wherein the membrane permeable to water has afiltering effect.
 7. The device according to claim 1, comprising aventilator (1) for providing a stream of gas for ventilation at anoutlet (2), a hose for inspiration air (11) one end of which isconnected to the outlet (2), wherein one lumen (5) of the double-lumenendotracheal tube (4), at its end distal to the patient, is connected tothe other end of the hose for inspiration air (11), flow metersconnected to the ends distal to the patient of the two lumina (5, 6) formeasuring the streams of gas in the two lumina (5, 6) of theendotracheal tube (4), flow meters connected to the ends distal to thepatient of the two lumina (5, 6) for measuring the pressures at the endsdistal to the patient of the two lumina (5, 6), an evaluation means fordetermining the flow resistance in a lumen (5, 6) flowed through by gasbecause of the stream of gas measured therein and the pressuresmeasured, and a means for outputting an information about the flowresistance of the lumina (5, 6).
 8. The device according to claim 1wherein the flow meters and/or pressure sensors is/are integrated in theventilator (1).
 9. The device according to claim 1 wherein valve meansof the hose/hoses are connected with the environment and/or with eachother between the hose/hoses and the endotracheal tube (4).
 10. Thedevice according to claim 1, comprising a ventilator (1) for providing astream of gas for ventilation at an outlet (2), a hose for inspirationair (11) one end of which is connected to the outlet (2), a double-lumenendotracheal tube (4) one lumen (5) of which, at its end distal to thepatient, is connected to the other end of the hose for inspiration air,flow meters connected to the ends distal to the patient of the twolumina, a closable opening at the end distal to the patient of the lumenfor the stream of expired gas to sealingly introduce a suction catheterup to the tracheal end of the endotracheal tube (4), and a means forregulating the pressure in the lumen (6) which is not flowed through bygas.
 11. The device according to claim 1, comprising a ventilator (1)for providing a stream of gas for ventilation at an outlet (2), a hose(11) for inspiration air one end of which is connected to the outlet(2), a double-lumen endotracheal tube (4) one lumen (5) of which, at itsend distal to the patient, is connected to the other end of the hose(11) for inspiration air, a means for applying a high-frequencyoscillating pressure to the end distal to the patient of the lumen (5)of the endotracheal tube (4) for the gas to be inspired.